The compound, which is the product of the novel process of this invention is a skeletal muscle relaxant useful in the treatment of muscle spasms and other similar muscle disorders associated with or caused by injury, disease, or arising spontaneously of unknown etiology. The compound and its utility are disclosed in U.S. Pat. No. 4,112,112, the disclosure of which is incorporated herein by reference. The process in U.S. Pat. No. 4,112,112 for preparing the compound of interest also comprises the dehydration of the same intermediate carbinol as utilized in the present invention. However, the dehydration in the prior art process is conducted at 0.degree. to 100.degree. C. which results in a mixture of the E and Z isomers. These isomers are separable by chromatography on an adsorbent such as silica gel and elution with a suitable solvent. From a commercial standpoint this is a very expensive, labor intensive unsatisfactory operation.
Now with the present invention there is provided a novel process wherein the dehydration is conducted at about -90.degree. C. to -50.degree. C. whereby the ratio of the E:Z-isomers is greater than about 95:5 from which the substantially pure E-isomer is readily available without the need for chromatographic purification, as in the prior art processes.